The isolation of biomolecules, such as proteins and peptides, has become of an increased interest during the past years. Some biomolecules need to be isolated as a last step of a biotechnological method for the production thereof, for example in the preparation of protein-based pharmaceutical compounds. Similarly there is also a need to separate biomolecules for analytical purposes in order to be able to quantitate and identify the proteins and/or peptides present in a sample. Electrophoretic methods are commonly used in the separation step.
Loading of samples onto electrophoretic gels may be done in different ways. The most common way is to provide the sample solution with a heavy medium and load the mixture in the bottom of a preformed well in the electrophoretic gel or by applying the sample solution onto paper strips placed on an vertical electrophoretic gel. Other ways of sample loading, used in for example isoelectric focusing, is cup loading or paper bridge loading.
Many analytical and preparative electrophoretic techniques are sensitive for sample contents and the results are often affected in a negative way by unwanted high abundant proteins. The bad influence can have several origins, such as sample preparation and/or sample application techniques.
It would be desirable to have control of both the sample content by for example specific enrichment and the sample application, preferably at the same time, which would increase the quality as well as the reproducibility of the results. It would be convenient to combine the sample preparation and application to have only one sample preparation-application step and this will also reduce losses of sample.
Magnetic beads are a convenient format which enables enrichment/capture from a large sample volume which is concentrated to a small amount before analysis.